I have a dog who loves to chase balls I throw in my backyard. After a nice long throwing session in the wet backyard, my dog’s tounge is completely black from the mud that gets on the ball. Is this bad for her?
Probably not. Unless you have a lot of wild animals in your yard and your dog may be ingesting their feces or you chemically treat your lawn, dirt is pretty harmless.
Two of my dogs love dirt. Every once in a while, both of them will eat a moutful of it. I figure they’re probably going off some instinct which tells them to do it it get minerals.
Now, if your dog is eating dirt all the time, that can be a problem called “pica.” (My youngest had it when she was a pup. She grew out of it.) It’s not necessarily the dirt that’s harmful-- it’s the compulsive behavior behind it. (Though if they’re eating a lot of it they can get digestive problems as a result.)
In general no. Your dog should be fine. Of course various nasty things might end up in the mud (fertilizers, pesticides, what-have-you) which would not be good for her but by and large a bit of dirt on the tongue from a good session of chasing the ball should cause no harm. My dogs did the same and it never troubled them and they all lived to ripe old ages.
My dog used to eat dirt fairly often. I think he actually liked the tender grass roots, and the dirt was just accepted as part of the cost.
His teeth did wear some from the grit in the dirt, but were still serving him OK when I had to have him put down at 15 + years. (ancient for a lab)